This invention relates to a method for producing improved baseball bats. More particularly, the invention relates to improvement in baseball bat manufacturing by which baseball bats having respective hardened hitting zones and which are difficult to break are produced.
In baseball bat manufacturing, hard wood is generally selected since a ball may be driven a greater distance with a bat having a harder surface. In view of this fact, aluminum bats have been also produced and sold in recent years. The process for producing aluminum bats is, however, totally unified, so that a large variety of aluminum bats are difficult to produce. In this regard, since wooden bats are produced by cutting wooden material, a bat complying with any person's wishes can be advantageously produced. However, wooden bats have other drawbacks that they are liable to split along the grain and to break across the grain when they receive excessive force. As the method for eliminating these disadvantages of wooden bats, there is well known a method to impregnate thermosetting resin into wood and to treat with heat and pressure as disclosed in Japanese Patent Publication Nos. 4961 of 1963 and 1279 of 1958.
In this process, there are two purposes of compression, one is to break up the wood surface structure and other is to improve the density of wood. When the wood surface structure is broken down, the wood grain mingles with the remaining wood portions and when the wood in this condition it is solidified with resin, the wood grain becomes difficult to peel off. The resin fills up the void spaces of grain to increase the density and as a result the hardness of wood is increased. Thus a bat which hits a ball to a distance and is rarely broken may be produced.
In the conventional art, this object has been attained by compressing wood material in the direction of wood grain layers using a pair of mold halves. By this method, the material receives the force in the direction of working of the molds, however, the force in the direction at a right angle to the mold working direction cannot be sufficiently effected. Therefore uneven compression of the material is caused to occur. Another disadvantage of the molds of this type is that the bat is slightly swollen in the direction perpendicular to the compressing direction because the bat is squeezed by a pair of molds, and the wood material swells out through the gaps of the molds which reduces the commercial value of the products.